package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class simpleExecutor implements Executor{

    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        // 1. 注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2 获取sql语句 select * from user where id = #{id} and username = #{username}
            // 转化sql语句： select * from user where id = ? and username = ?. 转换的过程中，还需要对#{}里面的值进行解析保存
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3. 获取预处理对象： preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());


        // 4. 设置参数
        String parameterType = mappedStatement.getParameterType();
        Class<?> parametertypeClass = getClassType(parameterType);


        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            // 当参数类型是包装类或String时，不需要反射，直接赋值
            if (isWrapClass(parametertypeClass) || parametertypeClass == String.class) {
                preparedStatement.setObject(i+1, params[0]);
                continue;
            }

            // 反射
            Field declaredField = parametertypeClass.getDeclaredField(content);
            // 暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            
            preparedStatement.setObject(i+1, o);

        }

        // 5. 执行sql
        // 获取mappedStatement的执行标签select, update..
        String opTagName = mappedStatement.getOpTagName();
        if (!opTagName.equals("select")) {
            preparedStatement.executeUpdate();
            return null;
        }

        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);
        ArrayList<Object> objects = new ArrayList<>();


        // 6. 封装返回结果集
        while (resultSet.next()) {
            Object o = resultTypeClass.newInstance();
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                String columnName = metaData.getColumnName(i);
                Object value = resultSet.getObject(columnName);
                
                // 使用反射或内省，根据数据表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);
            }

            objects.add(o);
        }


        return (List<E>) objects;
    }

    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if (parameterType != null) {
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        }

        return null;
    }

    private  boolean isWrapClass(Class clz) {
        try {
            return ((Class) clz.getField("TYPE").get(null)).isPrimitive();
        } catch (Exception e) {
            return false;
        }
    }

        /**
         * 完成对#{}的解析工作： 1。将#{}使用？进行代替 2。 解析出#{}里面的值进行存储
         * @param sql
         * @return
         */
    private BoundSql getBoundSql(String sql) {
        // 标记处理类：
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        String parseSql = genericTokenParser.parse(sql);
        // #{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);

        return boundSql;

    }
}
